The only place you will have canning supplies in So Cal that I am aware of is OSH. This time of year with the cucumbers coming in, they might just have it.
But I know more than one reefer who went for the food grade kalk buy a couple years back and had horrible hair algae problems while using it. The pharma grade is not that much more expensive, so unless you go through a LOT of kalk, it's not worth saving $5 a year to take the risk..